During certain surgical procedures, such as cardiologic procedures, various fluid reservoir devices are used. For example, during cardiopulmonary bypass, cardiotomy reservoirs, venous reservoirs, arterial reservoirs, suction canisters, and the like, are used to contain blood at selected points throughout the circuit. Various reservoirs may serve to temporarily hold blood or other fluids, solids, or semi-solids, and may provide additional functions, such as oxygenation, filtration, air removal, and the like. Additionally, if used as a suction canister, a reservoir may have a vacuum line hooked to an external vacuum source to create a negative pressure within the reservoir, and a patient line of tubing and an end cannula piece for removing fluids, matter, etc., from a surgical site.
A simplified example extracorporeal circuit, such as may be used during cardiopulmonary bypass procedures, provides a cannula inserted into the patient's venae cavae and tubing coupling the cannula to a venous reservoir. From the venous reservoir, blood is pumped through one or more oxygenators, filters, and/or heat exchangers prior to delivery through an arterial cannula back to the patient. A cardiotomy reservoir may be used to receive blood suctioned from the surgical site and/or blood from within the extracorporeal circuit, such as from the venous reservoir, for additional filtering and gas removal. An arterial reservoir may be used to receive blood immediately prior to delivery to the patient, providing additional control over delivery flow rates and volume.
Reservoirs used as components in extracorporeal circuits, such as cardiotomy, venous, and/or arterial reservoirs, generally are either open circuit or closed circuit systems. Open circuit cardiotomy reservoirs are conventionally constructed as rigid reservoirs having a fixed size, shape, and volume. Open circuit reservoirs allow for the blood (or other biological fluid) to be in contact with air during use and are typically used as a passive drainage system, whereby gravity facilitates the fluid drainage into the reservoir. Open circuit cardiotomy reservoirs can reduce the amount of air in the venous line and can also compensate for varying or insufficient venous return levels. Rigid reservoirs used as open circuit cardiotomy reservoirs can be used in combination with vacuum augmented venous drainage, whereby a vacuum is applied to the rigid reservoir creating a negative pressure within to facilitate the venous drainage from the patient. Currently no collapsible means exist to allow for flat storage of any of the currently available open circuit, rigid reservoirs.
On the other hand, closed circuit reservoirs are typically made from flexible, non-rigid reservoir containers. Flexible containers can collapse when emptying, thus reducing the exposure of blood to air and preventing excess air from being pumped to the arterial side of the extracorporeal circuit and to the patient. Accordingly, most flexible containers are designed to collapse during use. However, currently available closed circuit, non-rigid reservoirs do not include an ability to expand the container and provide additional rigidity for use as a rigid or semi-rigid reservoir having a defined volume.
Fluid reservoirs can be constructed from disposable materials, such as from plastics or other polymers. While disposability presents many advantages, such as improving sterility and simplifying post-surgical cleaning, using disposable devices also requires storing and maintaining an increased inventory volume of the disposable devices. Thus, the physical size of the disposable devices may hinder the number of disposable devices kept in inventory and available on demand. Accordingly, limited size inventories may require frequent re-order and re-stocking, which may become impractical or increase costs. For example, rigid cardiotomy reservoirs may have a 3 Liter or larger capacity, thus taking up considerable space. Surgical suites and hospital stockrooms may be limited in their ability to stock large quantities of similar rigid reservoirs.
U.S. Pat. No. 4,443,220 describes a blood collection and transfer apparatus for use in autotransfusion. The apparatus of the '220 patent provides a collapsible bag with a stent adapted to hold it in distended form when desired, such as when a negative pressure is applied. However, the stent of the '220 patent has a circular base and a number of parallel tines extending upward from the base, over which loops of the bag may be placed. Thus, the stent of the '220 patent still presents the problem of unnecessarily occupying space during storage, because the stent cannot be collapsed or otherwise folded but is necessary for using the apparatus as a rigid or semi-rigid reservoir.
In another example, U.S. Pat. No. 5,935,093 describes a softshell cardiotomy reservoir. The apparatus of the '093 patent does not provide a rigid or semi-rigid reservoir with a defined volume to be used as an open system. Thus, while the softshell cardiotomy reservoir of the '093 patent may be collapsible, it is like any other non-rigid container, and cannot be used in place of a rigid container.
Accordingly, there exists a need for collapsible fluid reservoirs. There exists a further need for collapsible fluid reservoirs that collapse to a substantially flat configuration during storage and expand to define a volume during use as a rigid or semi-rigid reservoir.